Electrophysiological effects of intravenous sotalol in acute myocardial infarction: a double-blind placebo-controlled study.

Controlled studies of the electrophysiological effects of beta-blockade in acute myocardial infarction have not previously been published. In this controlled, double-blind study 20 patients were randomized to treatment with placebo or sotalol administered as a continuous infusion for 12 h. Programmed electrical stimulation was performed from the right atrium. After 60 min of infusion in the sotalol-treated patients (n = 10) there was a significant prolongation of sinus cycle length (+15%) and sinus node recovery time (+28%). The AV nodal effective refractory period was prolonged by 15% after 45 min of infusion. Variables reflecting myocardial repolarization, atrial effective refractory period and QT interval, were increased by 20% and 10%, respectively. In the placebo group, except at 12 h, there was a general pattern of slightly diminishing values for all measured variables. The electrophysiological changes in the sotalol-treated group could be explained by the combined Class II and III activities of this drug. The infusion of sotalol was well tolerated, and the anticipated electrophysiological and Class II and III antiarrhythmic effects were observed, despite the acute myocardial infarction.